Finite Element Analysis of an F-111 Lower Wing Skin Fatigue Crack Repair

摘要

In this report a three dimensional finite element (F. E.) model has beendeveloped for a structural detail in an F-111 lower wing skin. The location of interest is a fuel flow groove in the lower wing skin where cracking had occurred in service on aircraft A8-145. Detailed models were developed for (1) un-cracked structure; (2) he cracked structure and (3) the repaired structure, using bonded composite patch for the repair. The objective of this work is to validate the design analysis used by the RAAF, using an independent approach for the stress analysis. The F.E. model has been validated using strain gauge results from a full scale test wing. The results of the F.E. analysis are shown to compare favourably with closed form solutions used by the RAAF (RAAF Engineering Standard C5033) in the original design of the repair. Thus the present work provides a basis for confidence in the design procedures contained in RAAF Engineering Standard C5033.